The invention relates to a plastic bag of a thermoplastic material for packing loosely poured material comprising venting perforations having a smallest size of at most 150 .mu.m microns in the bag foil wall.
A plastic bag of polyvinylchloride of this type, in which the perforations are obtained by the action of needles on the plastic foil is known in the art. In this known plastic bag the diameter of the perforations is at most 1,000 .mu.m, and preferably 100 to 300 .mu.m, the distance between the individual perforations varies between 14 and 19 mm.
This known plastic bag presents the disadvantage that the perforations formed by the action of needles are generally large in diameter, which means that, particularly during packaging loosely poured materials particularly very fine materials such as cocoa, polyvinylchloride and lime, particles are able to escape to the exterior through the perforations.
Moreover, these perforations have rough edges, so that if the perforations are small in size, they become blocked by the packaged material particles, with the result that the residual air present in such a plastic bag is very slow to leave the bag. This residual air is always present as the materials to be packed are always introduced into the bag by means of a gaseous fluid, mainly air, so that after filling there is always a substantial amount of air between the fine particles of the material in the bag.
This is the reason that until now these plastic bags cannot compete with papers bags for packing these fine materials as said papers bags do not present the abovementioned disadvantage.